<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <input type="button" value="播放">

    <script>
        let input = document.querySelector('input');
        input.onclick = function() {
            if(input.value == '播放') {
                input.value = '暂停';
            } else if(input.value == '暂停') {
                input.value = '播放';
            }
        }
    </script>
</body>
</html>